Comparison of three series hybrid active power filter topologies

The most common problem arising in the supply network is current harmonics. They may cause harmonics in the supply voltage and create problems, for example, in the distribution network. Active and passive filters are the traditional way of filtering currents. However, both of these have some disadvantages, namely resonance and tuning problems in passive filters and lack of high power switches in active filters. Research has recently been done to combine active and passive filters. These combinations are called hybrid filters and their purpose is to work efficiently without the disadvantages characteristic of the active and passive filter used alone. This paper presents a comparison of three hybrid filter topologies. All hybrid filters included in the comparison are based on a series active power filter. The comparison between filters is made according to their capability to filter current harmonics in the case of nonlinear load at different operating conditions.